Research in microbiology最新文献

This study aimed to investigate unintended mutations introduced by the CRISPR/Cas9 genome editing system in Edwardsiella piscicida. Whole-genome sequencing was conducted on the wild-type E. piscicida NH1 and its alanine racemase knockout mutants (E. piscicida Δalr325 NH1 and E. piscicida Δalr50 NH1) generated using CRISPR/Cas9 with a λ-Red recombineering system. Comparative genomic analyses revealed that the insertion sequence 1 (IS1) transpositions occurred in the CRISPR/Cas9-edited mutants, disrupting the type I restriction-modification system subunit M gene, in addition to the targeted gene deletion. Interestingly, no IS1 transpositions were detected in mutants produced via conventional plasmid-based allelic exchange, indicating the potential link between CRISPR/Cas9-mediated editing and transposition events. These results suggest that genome editing via CRISPR/Cas9 could trigger IS1 transposition, potentially due to double-stranded DNA breaks. The lack of sequence similarity between the single guide RNA (sgRNA) and the transposed regions suggests that transpositions are not CRISPR/Cas9 off-target effects. This study provides evidence of interactions between mobile genetic elements and genome editing systems, requiring further investigation into their underlying mechanisms.

A key component of microbial communication, autoinducer-2 (AI-2) signaling, affects several physiological processes, including environmental adaptation and biofilm formation in lactic acid bacteria (LAB). The multifarious contribution of AI-2, synthesized by LuxS, in improving biofilms and tolerance to hostile conditions in LAB has been investigated in this review. The evolutionary conservation and diversity of AI-2 are shown by a phylogenetic analysis of luxS gene among several LAB species. Furthermore, AI-2 signaling in LAB improves resistance to unfavorable environmental factors, including pH fluctuations, temperature extremes, and antimicrobial agents. Lactic acid bacteria could set off defenses against harmful impacts from environmental stresses.

Azospirillum brasilense is a PGPR that produces the phytohormone IAA, a signaling molecule involved in bacteria-plant interaction processes. IAA biosynthesis in Azospirillum is mainly carried out via the IPyA pathway in which the enzyme phenylpyruvate decarboxylase encoded by the ipdC gene is the main. The promoter region of ipdC gene contains cis elements that are highly conserved among different Azospirillum strains. In this work, we identified two proteins that interact with the promoter region of the ipdC gene, named MibR and LibR that belong to the MarR and LuxR transcriptional regulators family, respectively. Both proteins have an HTH domain, and in the case of LibR, it has a REC domain, with aspartic acid residue conserved in positions 7, 8 and 54, this last as a possible phosphorylation target. To explore their participation in the regulation of the ipdC gene, mutants of libR, mibR, and libR-mibR double mutant were generated. The results showed a decrease in IAA biosynthesis that was related to the observed decrease in ipdC gene expression mostly in the doble mutant compared with the wild type. In this work we suggest that ipdC transcription is regulated by LibR and MibR, providing new findings insight into the mechanism employed by A. brasilense to control IAA biosynthesis.